1. Field of the Invention
The present invention relates to valves, such as may be used in fuel injectors and other applications.
2. Prior Art
A typical application of the present invention is in spool valves, which are finding increasing use in diesel fuel injectors. See for instance U.S. Pat. No. 5,460,329, the disclosure of which is hereby incorporated by reference. Such spool valves are usually used to control the flow of engine oil to and from an intensifier and/or for direct needle control, or to engine valve actuators in a camless engine, though may also be used for other applications, such as in electro-hydraulically controlled camless engine applications.
In the case of starting an engine in cold weather, particularly a diesel engine, spool valves may become sluggish or even stick, or at least there is a fear that this will occur, complicating the starting process. Accordingly, when the engine temperature falls below a predetermined temperature, starting may be delayed by perhaps 10 or 15 seconds while the spool valves are rapidly actuated, heating the actuating coil or coils as well as providing assurance that the spool is free to move as commanded. This, however, solves only part of the problem, in that once cranking of the engine starts, cold engine oil (or fuel) being controlled by the spool valve tends to re-chill the valve to its original temperature.
There are of course many other applications wherein some of the same or similar problems are encountered, and in which the present invention may be applied.